1. Technical Field
The present invention relates to a printing apparatus of which a facsimile apparatus, a copying machine, or a printer of an Office Automation Apparatus is representative, a printing control program, and a printing control method. Particularly, the invention relates to an ink jet type printing apparatus in which particles of liquid ink of plural colors are ejected-on printing paper (recording medium) thereby to draw the predetermined character and image, a printing program, a printing method and printing data generating apparatus, a printing data generating program, a printing data generating method, and a recording medium storing the programs.
2. Related Art
Generally, ink jet type printing apparatuses (hereinafter referred to as an “ink jet printer”) can readily obtain a high quality color printing at a low cost. Therefore, with the spread of personal computers and digital cameras, this type of printing apparatus has been widely applied not only in offices but also by general users.
In such an ink jet printer, generally, while a moving member referred to as a carriage which integrally includes an ink cartridge and a printing head reciprocates on a printing medium (paper) in a direction vertical to the paper feeding direction, a particle of liquid ink is ejected in the shape of a dot from a nozzle of the printing head, whereby the predetermined character and image are drawn on the printing paper and the desired printing is created. Since this carriage includes ink cartridges of four colors including black (black, yellow, magenta, and cyan) and a printing head for each color, not only monochromatic printing but also full color printing having combinations of each color can be readily performed. Further, an ink jet printer including ink cartridges of six, seven, or eight colors in which light cyan, light magenta, and the like are added to the above four colors has been put to a practical use.
Further, in the ink jet printer of such a type which executes printing while thus reciprocating the printing head on the carriage in the direction vertical to the paper feeding direction, it is necessary to reciprocate the printing head from several times to one hundred times or more to finely print the entire page,. Therefore, this type of ink jet printer has a deficiency in that it takes a long printing time, compared with another type printing apparatus, for example, a laser printer using electrophotography of a copying machine. This type of ink jet printer is generally referred to as a “multipass type printer”.
In contrast, in an ink jet printer which has a long printing head and does not use a carriage, printing in which the printing head is moved in the width direction of printing paper by one scanning (one pass) is possible. Therefore, high speed printing similar to that in a laser printer can be performed. Further, since a carriage which mounts a printing head and a drive system for moving the carriage are not required, the size and weight of a printer housing can be reduced. Further, this ink jet printer also has an advantage in that noise reduction improves greatly. This type of ink jet printer is generally referred to as a “line head type printer”.
The printing head essential to such an ink jet printer has minute nozzles with a diameter of about 10 to 70 μm. The nozzles are spaced in a row or in plural rows in the printing direction. Therefore, due to unevenness during manufacturing, the ink ejecting direction of a partial nozzle tilts, or the nozzle is arranged out of an ideal position, so that a dot formed by that nozzle can be off a target point (ideal impact position). A so-called “splash bending phenomenon” can be produced.
As a result, in the printing portion corresponding to that bad nozzle part, bad printing referred to as a so-called “banding (streak) phenomenon” is produced, and printing quality can be greatly reduced. Namely, in case that the “splash bending phenomenon” is produced, the distance between the adjacent dots becomes uneven. In a portion where the distance between the adjacent dots is long, a “white streak (in case of white printing paper)” is produced; and in a portion where the distance between the adjacent dots is short, a “dark streak” is produced.
Particularly, such a banding phenomenon is easier to be remarkably produced in the “line head type printer” in which the printing head is fixed (one pass printing is performed) than in the “multipass type printer.” In the multipass type printer, the white streak is made inconspicuous by reciprocating the printing head many times.
Therefore, in order to prevent bad printing by such a “banding phenomenon”, improvement in manufacturing the printing head or improvement of its design, that is, research and development in hardware has been eagerly performed. However, it is difficult, due to manufacturing cost, printing quality, and current technology, to provide a printing head in which the “banding phenomenon” is eliminated.
Therefore, at present, in addition to the improvement in the hardware, a software method such as the printing control described below is used, whereby such a “banding phenomenon” is reduced.
For example, in JP-A-2002-19101 and JP-A-2003-136702, in order to meet the unevenness of the nozzle and the non-ejection of ink, in a portion which is low in density, shading correction is used to meet the unevenness of the head, and in a portion which is high in density, another color is substitutively used thereby to make banding and unevenness inconspicuous.
Further, in JP-A-2003-63043, regarding a solid image, that is, an image to be formed by shooting ink on the entire paper so that a white surface of the printing paper is invisible, a method of increasing the ink ejection amount from a nozzle adjacent to the pixels neighboring the non-ejection nozzle to form the solid image by all the nozzles is adopted.
However, in the method of reducing the banding phenomenon and the unevenness by using another color like the former related art, the hue of the portion subjected to the processing changes. Therefore, this method is not suitable for printing color photographic images or the like where a high quality image is required.
Further, in the portion which is high in density, the method of avoiding the “white streak phenomenon” by distributing the information of the non-ejection nozzle to the left and right, in case that this is applied to the “splash bending phenomenon”, is effective. However, there is a problem that banding remains in the portion-which is high in density.
On the other hand, a method like the latter related art has no problem when printing a solid image. However, when printing a halftone image, this method cannot be used. Further, when the method of filling a fine line with another color is used a little, there is no problem. However, in an image in which other colors continuously appear, similarly to the former method, there remains a problem that, the hue of a part of the image changes.